You are not required to use a migration agent to lodge a visa application.
Within Australia -
Still if you need help you can seek assistance from Mara Agents who are registered with the Office of the Migration Agents Registration
Authority (Office of the MARA) unless they are exempt. If you use a migration agent, it is strongly recommended to use a registered agent.
Note - Migration agents outside Australia
Migration agents who operate outside Australia do not have to be registered. The department may give some overseas agents an ID number. This number does not mean that they are registered.